The triose phosphate-3-phosphoglycerate-phosphate translocator from spinach chloroplasts: nucleotide sequence of a full-length cDNA clone and import of the in vitro synthesized precursor protein into chloroplasts.

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The nucleotide sequence of several cDNA clones coding for the phosphate translocator from spinach chloroplasts has been determined. The cDNA clones were selected from a lambda gt10 library prepared from poly(A)+ mRNA of spinach leaves using oligonucleotide probes modeled from amino acid sequences of tryptic peptides prepared from the isolated translocator protein. A 1439 bp insert of one of the clones codes for the entire 404 amino acid residues of the precursor protein corresponding to a mol. wt of 44,234. The full-length clone includes 21 bp at the transcribed non-coding 5' region with the ribosome initiation sequence ACAATGG, a 1212 bp coding region and 199 bp at the non-coding 3' region excluding the poly(A) tail which starts 17 bp downstream from a putative polyadenylation signal, AATAAT. According to secondary structure predictions the mature part of the chloroplast phosphate translocator exhibits high hydrophobicity and consists of at least seven membrane-spanning segments. Using plasmid-programmed wheat germ lysate the precursor protein was synthesized in vitro and could be imported into spinach chloroplasts where it is inserted into the inner envelope membrane.

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